1. Field of the Invention
The present invention relates generally to coating applicators for applying matrix material to a plurality of optical fibers to produce an optical fiber ribbon. In particular, the present invention relates to a coating applicator for establishing and maintaining desirable geometric characteristics while matrix material is applied to the optical fibers.
2. Discussion of Related Art
In optical fiber ribbon, it is desirable that the optical fiber ribbon have certain geometric characteristics. First, it is desirable to arrange the optical fibers in a planar relationship, which is generally achieved by minimizing the distances between the radial center point of each individual optical fiber and a straight line passing through the optical fibers. Second, it is desirable to uniformly coat the optical fibers so as to minimize variations in the coating thickness. Finally, it is desirable to reduce the gap between optical fibers and keep the gap between optical fibers to a minimum.
Ribbon geometry is important for several reasons. First, if the optical fibers of one ribbon are arranged in a plane and it is desired to splice that ribbon with another ribbon also having optical fibers arranged in a plane, the individual optical fiber ends will be aligned when the two ribbon ends are spliced together, thereby establishing a connection which will efficiently transmit light. Furthermore, if the geometry is uniform and/or if the gap between optical fibers is minimized more ribbons can be stacked in a given space within a cable.
Uniform geometry also reduces the stress experienced by the optical fibers when the cable containing a ribbon is bent or compressed. Such bending and compression may cause the cable components to contact one another in various ways. Such contact applies forces to the external ribbon surface. Irregularities in the ribbon, such as non-uniform coating thickness, may result in one optical fiber experiencing a greater stress than other optical fibers. However, if the ribbon has fewer irregularities, these forces will be distributed over the external ribbon surface and among the optical fibers more evenly.
Prior art coating applicators, such as the resin coating die disclosed in Japanese Patent No. 6-63483(A), for production of optical fiber ribbon permit a plurality of optical fibers to pass through a chamber in which matrix material is applied to the optical fibers. The chamber has an opening through which the optical fibers pass. To achieve some degree of the desirable geometric characteristics, some prior art applicators have a die with a chamber therein which has an opening which is only slightly larger than the optical fiber ribbon. If the opening in the chamber of such a prior art applicator contacts the optical fibers so as to achieve the desirable geometric characteristics described above, the optical fibers may be abraded or pinched as they move through the narrow opening because the optical fibers are bounded on all sides by the narrow opening. However, if the opening does not contact the optical fibers, the geometry of the optical fiber ribbon will be less desirable because the optical fibers are free to move within the opening and within the chamber.
Accordingly, it is an object of the present invention to provide a coating applicator which produces an optical fiber ribbon with improved geometry.
The foregoing objective is realized by the present invention which comprises a coating applicator for continuously applying matrix material to a plurality of optical fibers arranged in a ribbon configuration. The coating applicator has a first contacting means for contacting the plurality of optical fibers on a first side of the plurality of optical fibers and for contacting a first end fiber of the plurality of optical fibers. The coating applicator also has a second contacting means for contacting the plurality of optical fibers on a second side of the plurality of optical fibers and for contacting a second end fiber of the plurality of optical fibers. The second contacting means is located downstream of the first contacting means, and is located relative to the first contacting means so that the optical fibers are forced to contact the first and second contacting means as described above.
One coating applicator according to the present invention includes a die containing a preliminary matrix material application chamber having a matrix material supply orifice. The preliminary matrix material application chamber has a first preliminary chamber side containing an entrance opening and a second preliminary chamber side containing an exit opening, the second preliminary chamber side being opposite the first preliminary chamber side. The preliminary chamber entrance opening defines a first guide edge for contacting the plurality of optical fibers on a first side of the plurality of optical fibers and for contacting a first end fiber of the plurality of optical fibers. The die further contains a main matrix material application chamber also having a matrix material supply orifice. The main matrix material application chamber has a first main chamber side containing an entrance opening for receiving the optical fibers from the preliminary chamber exit opening and has a second main chamber side containing an exit opening. The second main chamber side is opposite the first main chamber side. Furthermore, the main chamber entrance opening defines a second guide edge for contacting a second side of the plurality of optical fibers and for contacting a second end fiber of the plurality of optical fibers. Finally, the main chamber entrance opening is offset relative to the preliminary chamber entrance opening such that the optical fibers contact the first and second guide edges as described above.
Another applicator according to the present invention includes a die containing a chamber having a matrix material supply orifice. The chamber has a first side containing an entrance opening and a second side containing an exit opening, the second side being opposite the first side. The entrance opening defines an entrance guide edge for contacting the plurality of optical fibers on a first side of the plurality of optical fibers and for contacting a first end fiber of the plurality of optical fibers. Disposed within the chamber is a pin, the pin having a pin guide edge for contacting the plurality of optical fibers on a second side of the plurality of optical fibers and for contacting a second end fiber of the plurality of optical fibers. In this die, the pin is offset relative to the entrance opening such that the optical fibers contact the entrance and pin guide edges as described above.
Other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description read in conjunction with the attached drawings and claims appended hereto.